1. Field of the Invention
The present invention relates to a control circuit for motor of electric jogging device, and more particularly to a control circuit to ensure the user's safety.
2. Description of the Prior Art
The conventional electric jogging device is designed as FIG. 1 shows. It mainly includes a unit body 10 whose basis is fitted with a motor and a transmission mechanism (not shown) in order for a motor control circuit inside of an electronic gauge panel 12 to drive the motor and the transmission mechanism in rotation when the power switch 11 is turned on, whereby the runway band 13 starts the cyclic rotation. Accordingly, the user is able to stand thereon to make a jogging exercise.
The basic control circuit for conventional motors is shown in FIG. 2. It mainly includes a power switch 21 between a power input terminal 20 and an electronic loop 22. The other side of the electronic loop 22 has a safety system loop 23 with a safety plug-in pin 24. Besides, the electronic loop 22 is connected with a control panel 25 so as to control the operation of the motor 26.
Referring to FIGS. 1 and 2, the safety plug-in pin 24 of the above-mentioned safety system loop 23 is, in fact, a power sensing wire 15 with a plug-in terminal 14 and is plugged in the plug-in hole 16 of the safety system loop 23 of the electronic gauge panel 12 and appears outside of the unit body 10. The other end is a clamp 17 to clamp on the body of the user. Therefore, when the user wishes to use this unit 10, the plug-in terminal 14 of the safety plug-in 24 has to be inserted into the plug-in hole 16 so that the electronic loop 22 will normally supply power to the control panel 25 and the motor 26 for performing the pre-arranged circuit control procedure. In another words, when the plug-in terminal 14 of the safety plug-in pin 24 separates from the plug-in hole 16 due to slipping or another accidents of the user, the safety system loop 23 will send this message to the electronic loop 22 to order the control panel 25 to stop to supply power to the motor 26. Accordingly, the runway band 13 won't run around any more.
Although the expected effect is able to be reached with this conventional safety control method, it still has disadvantages. When the safety plug-in pin 24 separates from the plug-in hole 16, the power input terminal 20 still supplies power to the electronic loop 22 (because the power switch 21 is till in ON-state). In short, if a malfunction happens to the safety system loop 23, this message can't exactly be sent to the electronic loop 22. Therefore, the control panel 25 and the motor 26 continue to be in operation to result in a high danger.
A number of reasons accounts for the malfunction of the safety system loop 23, e.g. the electronic parts are wet, burnt down or its use is beyond the expiry date.